[Issue 19721] Cannot take address of scope local variable even with dip1000 if a member variable is a delegate

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19721

Walter Bright <bugzilla at digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
           Hardware|x86_64                      |All
         Resolution|---                         |INVALID
                 OS|Linux                       |All

--- Comment #3 from Walter Bright <bugzilla at digitalmars.com> ---
Here's what's happening. `scope int* s;` declares `s` as a pointer that must
not be allowed to escape `main()`. The `func(&s);` passes the address of `s` to
`func`. `func` declares its parameter as `scope int**`. This ensures that the
address of `s` does not escape, but says nothing about `s`'s pointer value,
which must not be allowed to escape. I.e. the value of `s` is not protected
from escaping `func`, so the call causes a compile error.

If `s` is simply declared as an `int`, the `scope` annotation for `s` is
meaningless, as there is no pointer value to protect, and it compiles
successfully.

----

Generally, rewriting perplexing examples as simple pointers tends to make what
is happening much easier to determine. A delegate is regarded as a pointer. A
struct that contains pointer values is itself regarded as a pointer. Hence the
simplification of the example.

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